Mobile and expandable firmware-based optical spectroscopy system and method for controlling same

ABSTRACT

Disclosed are a mobile and expandable firmware-based optical spectroscopy system and a method for controlling same. The optical spectroscopy system may comprise: a wearing part attached to a particular region of a subject to irradiate light, on the basis of a firmware, to the particular region and measure the bodily signals of the subject by collecting emergent light which has passed through the particular region; and a monitoring unit, connected to the wearing part via a wired or wireless network, for controlling the strength of the light irradiated from the wearing part.

FIELD OF THE INVENTION

The present invention relates to a mobile and expandable firmware-basedoptical spectroscopy system and a method for controlling the same.

BACKGROUND

When a living organism attempts to perform a certain action governed bya specific part of a cerebrum, or receives a stimulus associated withthe specific part of the cerebrum, neuron cells of the correspondingpart of the cerebrum is activated. For example, when perception,calculation, judgment, or the like is carried out, a frontal lobe of thecerebrum and neuron cells corresponding to the frontal lobe areactivated. At this time, in the peripheral blood vessels of theactivated cells, the concentration of oxyhemoglobin is increased andthat of deoxyhemoglobin is reduced in order to supply oxygen to theneuron cells. FIG. 1 shows an example in which the concentration ofoxyhemoglobin is increased and that of deoxyhemoglobin is reduced asneuron cells are activated.

Near-infrared spectroscopy (NIRS) can measure the concentration changesof oxyhemoglobin and deoxyhemoglobin caused by the activation ofneuronal cells. For example, a human body includes substances calledchromophores, which have a chemical structure that can well absorb lightof various kinds of specific wavelength bands. Hemoglobin is also a kindof the chromophores, and exhibits a larger degree of absorption thanwater in a near-infrared region. Since absorption coefficients ofoxyhemoglobin and deoxyhemoglobin vary with wavelengths in thenear-infrared region, information on the concentration changes ofoxyhemoglobin and deoxyhemoglobin in the desired region can be obtainedusing light of two wavelengths in the near-infrared region.

FIG. 2 shows an example of absorption factors of oxyhemoglobin anddeoxyhemoglobin, and FIG. 3 shows an example of a trajectory of lightinjected into a cerebrum.

First, FIG. 2 shows that the absorption coefficients of oxyhemoglobin(Oxy Hb) and deoxyhemoglobin (Deoxy Hb) are changed according to thewavelengths.

Further, FIG. 3 shows an example of a NIRS system by which light of anear-infrared region is emitted through a source (S) using a laser or alight emitting diode (LED) and the emitted laser or light is detected bya detector (D). Here, the light emitted by the source passes throughspecific parts of the brain along a curved path as shown in FIG. 3, andthe NIRS system can obtain information on the parts of the brain throughwhich the light has passed using information on the light detected bythe detector. Background information on the NIRS system is welldescribed in U.S. Patent Application Publication No. 2013/0256533.

SUMMARY OF THE INVENTION

One object of the invention is to provide a mobile and expandablefirmware-based optical spectroscopy system and a method for controllingthe same.

Another object of the invention is to provide an optical spectroscopysystem and a method for controlling the same, by which it is possible touse a pipeline-structured matched filter to implement a matched filterstructure for the same time as a bit period of input Walsh codes, andminimize current leakage and nonlinear effects occurring in a switchingcircuit.

Another object of the invention is to provide an optical spectroscopysystem and a method for controlling the same, by which it is possible touse time-divided spread spectrum codes (TDSSC) to reduce duration of 1of Walsh codes per unit time and inject more intense light, therebyincreasing the intensity of the light with the same total energy.

Another object of the invention is to provide an optical spectroscopysystem and a method for controlling the same, by which it is possible tomodulate light emitted from a plurality of light sources using Walshcodes and emit the modulated light, and detect light coming through aspecific region and demodulate the detected light using the Walsh codes,thereby distinguishing the light source that has emitted the light.

Another object of the invention is to provide an optical spectroscopysystem and a method for controlling the same, by which it is possible toaccumulate input signals using a reference clock used for light emissionas a sampling clock, thereby minimizing white Gaussian noise withoutadditional circuitry such as an additional phase locked loop (PLL).

Another object of the invention is to provide an optical spectroscopysystem and a method for controlling the same, by which it is possible toprocess, visualize, and control data in a monitoring device, and guidefirmware update according to the release of a new version of firmwareincluded in an attachment device such as a headset.

Another object of the invention is to provide an optical spectroscopysystem and a method for controlling the same, by which it is possible tocollect, manage, and analyze data measured through a web server andprovide personalized results through a monitoring device.

There is provided an optical spectroscopy system, comprising: anattachment unit attached to a specific region of a subject andconfigured to, based on firmware, emit light to the specific region andcollect light coming through the specific region to measure a biosignalof the subject; and a monitoring unit connected to the attachment unitthrough a wired or wireless network and configured to control anintensity of the light emitted by the attachment unit.

According to one aspect of the invention, the attachment unit comprises:a light transmission unit configured to emit light to the specificregion using at least one of a laser and a light emitting diode (LED); alight reception unit configured to detect light coming through thespecific region; and a main processing unit configured to control thelight transmission unit and the light reception unit based on thefirmware, and receive output data of the light reception unit.

According to another aspect of the invention, the firmware includes: (1)a function for controlling operations of the light transmission unit,the light reception unit, and the main processing unit; (2) a functionfor separating the output data received by the main processing unit fromthe light reception unit into optical data of each channel; and (3) afunction for controlling the attachment unit to transmit the separatedoptical data to the monitoring unit.

According to another aspect of the invention, the firmware furtherincludes: (4) a function for providing a firmware update mode to updatethe firmware and a firmware execution mode to execute the firmware.

According to another aspect of the invention, a plurality of lighttransmission modules included in the light transmission unit emit lightof different channels modulated with time-divided spread spectrum codes(TDSSC), and the firmware demodulates data for the light received by thelight reception unit based on the time-divided spread spectrum codes toseparate the output data into the optical data of each channel.

According to another aspect of the invention, the light transmissionunit comprises a plurality of light transmission modules, and each ofthe plurality of light transmission modules comprises: a light sourceincluding at least one of a laser and a light emitting diode (LED); acylinder in which the light source is inserted; a spring configured toprovide physical pressure to the cylinder in which the light source isinserted, such that the light source is brought into close contact withthe specific region of the subject; and a case within which the lightsource, the cylinder, and the spring is disposed.

According to another aspect of the invention, each of the plurality oflight transmission modules further comprises: a reference lightreception unit disposed on a side surface of the cylinder within thecase and configured to collect light coming through the specific region.

According to another aspect of the invention, the light reception unitcomprises a plurality of light reception modules, and each of theplurality of light reception modules comprises: a light detectorconfigured to collect light coming through the specific region; acylinder in which the light detector is inserted; a spring configured toprovide physical pressure to the cylinder in which the light detector isinserted, such that the light detector is brought into close contactwith the specific region of the subject; and a case within which thelight detector, the cylinder, and the spring is disposed.

According to another aspect of the invention, each of the plurality oflight reception modules further comprises a trans-impedance amplifier(TIA) inserted in the cylinder together with the light detector, and thelight collected by the light detector is converted into an electricalsignal and amplified by the TIA in a fully differential manner.

According to another aspect of the invention, in the attachment unit, anadditional function is added to the attachment unit by updating thefirmware.

According to another aspect of the invention, in the attachment unit, anarea in which the biosignal is measurable is expanded by adding a basicstructure, which is a H-hexagonal structure (HHS) composed of aplurality of light transmission modules and a plurality of lightreception modules.

According to another aspect of the invention, when the basic structureis added, the attachment unit updates the firmware to add an expandedfunction according to the added basic structure.

According to another aspect of the invention, the attachment unit isimplemented in the form of a headset attachable to a head region of thesubject.

According to another aspect of the invention, the optical spectroscopysystem further comprises: a web server configured to provide a newversion of firmware and accumulate data for the biosignal to manage andanalyze the data.

There is provided a method for controlling an optical spectroscopysystem, wherein the optical spectroscopy system comprises an attachmentunit and a monitoring unit, and wherein the method comprises the stepsof: by the attachment unit, determining whether the attachment unit isconnected to the monitoring unit; by the attachment unit, initializing asystem of the attachment unit according to a system on command; by theattachment unit, adjusting a gain of each channel for light of differentchannels emitted by the attachment unit, according to a calibrationstart command from the monitoring unit; by the attachment unit, emittinglight to a specific region of a subject according to a measurement startcommand from the monitoring unit, and collecting light coming throughthe specific region to measure a biosignal of the subject; and by theattachment unit, terminating the system of the attachment unit accordingto a measurement end command or a system off command from the monitoringunit.

According to the invention, it is possible to provide a mobile andexpandable firmware-based optical spectroscopy system and a method forcontrolling the same.

According to the invention, it is possible to use a pipeline-structuredmatched filter to implement a matched filter structure for the same timeas a bit period of input Walsh codes, and minimize current leakage andnonlinear effects occurring in a switching circuit.

According to the invention, it is possible to use time-divided spreadspectrum codes (TDSSC) to reduce duration of 1 of Walsh codes per unittime and inject more intense light, thereby increasing the intensity ofthe light with the same total energy.

According to the invention, it is possible to modulate light emittedfrom a plurality of light sources using Walsh codes and emit themodulated light, and detect light coming through a specific region anddemodulate the detected light using the Walsh codes, therebydistinguishing the light source that has emitted the light.

According to the invention, it is possible to accumulate input signalsusing a reference clock used for light emission as a sampling clock,thereby minimizing white Gaussian noise without additional circuitrysuch as an additional phase locked loop (PLL).

According to the invention, it is possible to process, visualize, andcontrol data in a monitoring device, and guide firmware update accordingto the release of a new version of firmware included in an attachmentdevice such as a headset.

According to the invention, it is possible to collect, manage, andanalyze data measured through a web server and provide personalizedresults through a monitoring device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example in which the concentration of oxyhemoglobin isincreased and that of deoxyhemoglobin is reduced as neuron cells areactivated.

FIG. 2 shows an example of absorption factors of oxyhemoglobin anddeoxyhemoglobin.

FIG. 3 shows an example of a trajectory of light injected into acerebrum.

FIG. 4 is a block diagram showing an example of an optical spectroscopysystem according to one embodiment of the invention.

FIG. 5 shows an implementation example of a module constituting a lighttransmission unit according to one embodiment of the invention.

FIG. 6 shows an implementation example of a module constituting a lightreception unit according to one embodiment of the invention.

FIG. 7 shows examples of updating firmware with respect to fixedhardware to add a new function, and updating firmware to controlexpanded hardware according to one embodiment of the invention.

FIG. 8 is a flowchart showing a part of a method for controlling anattachment unit according to one embodiment of the invention.

FIG. 9 is a flow chart showing the remaining part of the method forcontrolling the attachment unit according to one embodiment of theinvention.

FIGS. 10 and 11 are flowcharts showing the control method for the casewhere firmware includes a function of determining how to adjust theseparation and gain of a channel according to one embodiment of theinvention.

FIG. 12 shows an example of a headset system according to one embodimentof the invention.

FIG. 13 shows an example of an expanded form of a headset systemcomposed of three basic structures according to one embodiment of theinvention.

FIG. 14 shows an expanded example of a headset system composed of ninebasic structures according to one embodiment of the invention.

FIG. 15 is a block diagram of Tx and Rx to which a matched filter for anoptical spectroscopy system is applied according to one embodiment ofthe invention.

FIG. 16 is a block diagram schematically showing an example in which amatched filter and a slope analog-digital converter are combinedaccording to one embodiment of the invention.

FIG. 17 shows an example of a matched filter applied in a pipelinestructure according to one embodiment of the invention.

FIG. 18 shows a time diagram in the matched filter applied in thepipeline structure according to one embodiment of the invention.

FIG. 19 shows a detailed schematic structure of a pipelinetransconductor (Gm) amplifier according to one embodiment of theinvention.

FIG. 20 shows a structure for calibrating a DC offset caused by a Gm-Cmismatch according to one embodiment of the invention.

FIG. 21 shows a dual current source structure for discharge in apipeline Gm-C structure according to one embodiment of the invention.

FIG. 22 shows a switching time diagram for a pipeline Gm-C based matchedfilter structure according to one embodiment of the invention.

FIG. 23 shows an example of an application aspect of CDMA modulationaccording to one embodiment of the invention.

FIG. 24 shows an example of an aspect of modulating changes in a bloodoxygen saturation level with codes according to one embodiment of theinvention.

FIG. 25 shows an example of a flowchart for extracting a hemodynamicsignal except for low noise when proceeding with code-based modulationand demodulation according to one embodiment of the invention.

FIG. 26 shows an oversampling effect and a matched filter effectaccording to one embodiment of the invention.

FIG. 27 shows a comparison between a matched filter structure of priorart and that according to one embodiment of the invention.

FIG. 28 shows an application example of time-divided spread spectrumcodes according to one embodiment of the invention.

FIG. 29 shows structures of a dual wavelength laser driver and a LEDdriver according to one embodiment of the invention.

FIG. 30 shows a drive control signal level shifter according to oneembodiment of the invention.

FIG. 31 shows a laser driver using time-divided spread spectrum codesaccording to one embodiment of the invention.

FIG. 32 is a flowchart showing an example of a method for automaticfirmware update according to one embodiment of the invention.

FIG. 33 shows functions for updating firmware according to oneembodiment of the invention.

FIG. 34 shows functions for processing big data according to oneembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings.

Mobile and Expandable Firmware-Based Optical Spectroscopy System

FIG. 4 is a block diagram showing an example of an optical spectroscopysystem according to one embodiment of the invention.

As shown in FIG. 4, an optical spectroscopy system 400 may comprise anattachment unit 410, a monitoring unit 420, a user server 430, and a webserver 440. Here, there may be a plurality of systems each comprisingthe attachment unit 410, the monitoring unit 420, and the user server430, and each of the plurality of systems may be implemented tocommunicate with the web server 440 and receive services from the webserver 440. For example, the optical spectroscopy system 400 may beimplemented such that a first system comprising a first attachment unit,a first monitoring unit, and a first user server, and a second systemcomprising a second attachment unit, a second monitoring unit, and asecond user server communicate with the web server 440, respectively, orsuch that three or more systems communicate with the web server 440,respectively. According to another embodiment of the invention, theoptical spectroscopy system 400 may also be implemented to comprise onlythe attachment unit 410, the monitoring unit 420, and the user server430. The attachment unit 410, the monitoring unit 420, the user server430, and the web server 440 may be connected to each other through awired or wireless network to transmit and receive data.

The attachment unit 410 may be implemented in the form of a deviceattached to a specific part of a user (e.g., an upper end of the user'shead). For example, the attachment unit 410 may be implemented in theform of a headset and worn on a region of the user's head to bemeasured. The attachment unit 410 may comprise a light transmission unit411, a light reception unit 412, and a main processing unit 413. Asshown in FIG. 4, the main processing unit 413 may comprise a controlunit 413 a and a firmware 413 b.

The light transmission unit 411 may comprise at least one modulecomposed of a circuit that actually produces light. For example, thelight transmission unit 411 may comprise one or more modules (e.g., alight transmission module 500 to be described below with reference toFIG. 5) implemented to include a laser, or configured to include a lightemitting diode (LED) and a LED drive circuit.

The light transmission unit 411 may use multi-wavelength light in a bandof wavelengths from 600 nm to 1300 nm, and may comprise a plurality oflight sources that emit the multi-wavelength light. Here, the intensityof the light emitted from the light transmission unit 411 may be changedby the monitoring unit 430. Further, the intensity of the light emittedfrom the light transmission unit 411 may be changed according to achange in the magnitude of current inputted to the laser or the LED, achange in the frequency of light injected into a living organism for apredetermined period of time, or the like.

FIG. 5 shows an implementation example of a module constituting a lighttransmission unit according to one embodiment of the invention. Thelight transmission unit according to the present embodiment maycorrespond to the light transmission unit 411 described with referenceto FIG. 4.

A light transmission module 500 may correspond to a light sourceincluded in the light transmission unit 411 to emit light. As shown inFIG. 5, the light transmission module 500 may comprise a bolt 510, aspring 520, a light source 530, a cylinder 540, a reference lightreception unit 550, and a case 560.

The light source 530 may be implemented in the form of a laser, a LED orthe like disposed on a PCB, and inserted in the cylinder 540. Thereference light reception unit 550 may be coupled to a side surface ofthe cylinder to detect light received through a head surface of a user.The light detected by the reference light reception unit 550 may also beused to measure a biological change of the user.

The spring 520, the light source 530, the cylinder 540, and thereference light reception unit 550 may be disposed within the case 560.The case 560 may be implemented such that the top and bottom thereof arecoupled to each other through the bolt 510.

The cylinder 540 may be structured such that it is pushed by the spring520 in a downward direction in FIG. 5. When a subject wears a productlike the attachment unit 410 on his/her head, the spring 520 may be usedto prevent widening of the gap between the light transmission unit 411and the subject. For example, the cylinder 540 or the reference lightreception unit 550 may be brought into close contact with a measuredregion of the subject by the force of the spring 520, regardless of theshape or curvature of the measured region of the subject.

The above configuration enables consistent measurements because lightcan be emitted to the subject while the close contact is constantlymaintained, regardless of the state of the measured region of thesubject, the gap between the measured region and the attachment unit 410(such as a headset), or the like. Further, it is possible to decreasethe influence of a movement of the subject or a minute movement of theattachment unit 410 on the light transmission, and to reduce the outwardleakage of the emitted light.

Referring again to FIG. 4, the light reception unit 412 may comprise atleast one module (e.g., a light detection module 600 to be describedbelow with reference to FIG. 6) composed of a photo detector (PD) forcollecting light emitted from the light transmission unit 411 and comingthrough the living organism, and a circuit for driving the photodetector. The light emitted from the light transmission unit 411 may belight modulated with specific codes such as time-divided spread spectrumcodes (TDSSC). Here, when light from a plurality of light transmissionmodules is received by each module of the light reception unit 412, theoverlapped form of the TDSSC of the received light may be diverse. Thereceived light may be amplified through a plurality of steps, and theintensity of the received light is diversified according to variousconditions when the light is received. Thus, the light reception unit412 may have a variety of adjustable gains.

FIG. 6 shows an implementation example of a module constituting a lightreception unit according to one embodiment of the invention. The lightreception unit according to the present embodiment may correspond to thelight reception unit 412 described with reference to FIG. 4.

The light reception module 600 may be a module included in the lightreception unit 412 to receive light. As shown in FIG. 6, the lightreception module 600 may comprise a bolt 610, a spring 620, a detector630, a cylinder 640, and a case 650.

The detector 630 may comprise a trans-impedance amplifier (TIA) and aphoto detector (PD), and may be disposed within the cylinder 640. Thecase 650 may contain the spring 620, the detector 630, and the cylinder640. The case 650 may be implemented such that the top and bottomthereof are coupled to each other through the bolt 610.

The spring 620 may be included to push the cylinder 640 including thedetector 630 in a downward direction in FIG. 6. Similar to FIG. 5, thespring 620 may be used to bring the light reception unit 412 into closecontact with a measured region of a subject.

Light emitted by the light transmission unit 411 may be received by thedetector 630 and converted into an electrical signal. The electricalsignal is a signal amplified in a fully differential manner by the TIAincluded in the detector 630, and the signal outputted from the lightreception unit 412 may be inputted to the main processing unit 413included in the attachment unit 410.

The embodiments of FIGS. 5 and 6 are only intended to facilitateunderstanding of the invention, and the modules included in the lighttransmission unit 411 or the light reception unit 412 are not limited tothe embodiments of FIG. 5 or 6.

Referring again to FIG. 4, the main processing unit 413 may comprise thecontrol unit 413 a and the firmware 413 b. The firmware 413 b includedin the main processing unit 413 may provide the following functions (1)to (4):

(1) a function for appropriately controlling operations of the hardwareincluded in the attachment unit 410 (e.g., controlling the lighttransmission unit 411, the light reception unit 412, and the mainprocessing unit 413);

(2) a function for separating output data of an A/D converter on a Rxside included in the control unit 413 a into optical data of eachchannel;

(3) a function for transmitting the separated optical data to themonitoring unit 420 using wireless communication (e.g., Bluetooth orWi-Fi); and

(4) a function for providing a firmware update mode and a firmwareexecution mode through a customized boot loader, and allowing a user toselect either the firmware update mode or the firmware execution modethrough the user server 430.

The user server 430 may be a device of a user (e.g., an experimenter)for collecting and managing data, managing user information, andtransmitting the data to the web server 440 upon obtaining a subject'sconsent for information provision.

The attachment unit 410 according to the present embodiment may providethe above-described functions (1) to (4) through the firmware 413 b,thereby achieving the following two effects:

Firstly, when the hardware configuration of the attachment unit 410 suchas a headset is fixed, the firmware 413 b may be updated or changed sothat newly improved functions are instantly added and used in the mainprocessing unit 413, or the functions of the main processing unit 413are instantly changed and used, without changing the elements,structure, or the like of the hardware.

Secondly, when the hardware configuration of the attachment unit 410such as a headset may be expanded, the firmware may be updated orchanged to control the expanded hardware configuration, without havingto add a special circuit or hardware for driving the light transmissionunit 411 or the light reception unit 412, or change the circuit orhardware. Accordingly, the attachment unit 410 may be variably andfreely implemented in diverse structures, without being limited to thetype of hardware.

FIG. 7 shows examples of updating firmware with respect to fixedhardware to add a new function, and updating firmware to controlexpanded hardware according to one embodiment of the invention. Thefirmware according to the present embodiment may correspond to thefirmware 413 b described with reference to FIG. 4.

In FIG. 7, T and R may denote a light transmission module and a lightreception module, respectively. For example, a first configuration 710of FIG. 7 shows a headset structure that is fixedly configured to have aH-hexagonal structure (HHS) as a basic structure, by means of sevenlight transmission modules and twelve light reception modules. Further,a second configuration 720 of FIG. 7 shows an example in which theheadset structure is expanded to have ten light transmission modules andeighteen light reception modules.

Here, the firmware (e.g., the firmware 413 b) may be updated to add anewly improved function or to change an existing function, even in afixed state without changing the hardware configuration as in the firstconfiguration 710. The first configuration 710 shows an example in whichthe firmware having a function A is updated to the firmware having afunction A+B.

The second configuration 720 corresponds to an embodiment in which thehardware configuration of the headset is changed/expanded, and shows anexample in which the firmware having a function A is updated to thefirmware having a function A+C according to the expansion of thehardware.

Further, as described above, the light reception unit 412 may havevarious adjustable gains. Here, the function for adjusting the gains maybe included in the firmware 413 b or the monitoring unit 420.

FIG. 8 is a flowchart showing a part of a method for controlling anattachment unit according to one embodiment of the invention. Theattachment unit according to the present embodiment may correspond tothe attachment unit 410 described with reference to FIG. 4. Here, theattachment unit 410 may perform steps 810 to 870 under the control ofthe firmware 413 b.

In step 810, the attachment unit 410 may determine whether it isconnected to the monitoring unit 420. Here, when the attachment unit 410is connected to the monitoring part 420, it may perform step 820.

In step 820, the attachment unit 410 may determine whether a system oncommand is received. For example, the attachment unit 410 may performstep 830 when the system on command is received.

In step 830, the attachment unit 410 may initialize the system. Here,the system may be the attachment unit 410, or the optical spectroscopysystem 400 described with reference to FIG. 4.

In step 840, the attachment unit 410 may wait for a command from themonitoring unit 420.

Steps 850, 860 and 870 may indicate that the attachment unit 410 mayperform different operations according to commands from monitoring unit420. For example, in step 870, the attachment unit 410 may determinewhether a system off command is received, and may be terminated when thesystem off command is received. In other words, the method forcontrolling the attachment unit 410 according to the present embodimentmay be terminated according to the system off command from themonitoring unit 420.

In step 850, the attachment unit 410 may determine whether a calibrationstart command is received. Here, when the calibration start command isreceived, the attachment unit 410 may perform step 910 of FIG. 9 or step1012 of FIG. 10. Step 910 may be performed when the function ofdetermining how to adjust the separation and gain of a channel is notincluded in the firmware 413 b but in the monitoring unit 420. Further,step 1012 may be performed when the function of determining how toadjust the separation and gain of a channel is not included in themonitoring unit 420 but in the firmware 413 b.

In step 860, the attachment unit 410 may determine whether a measurementstart command is received. Here, when the measurement start command isreceived, the attachment unit 410 may perform step 960 of FIG. 9 or step1110 of FIG. 11. Step 960 may be performed when the function ofdetermining how to adjust the separation and gain of a channel is notincluded in the firmware 413 b but in the monitoring unit 420. Further,step 1110 may be performed when the function of determining how toadjust the separation and gain of a channel is not included in themonitoring unit 420 but in the firmware 413 b.

FIG. 9 is a flow chart showing the remaining part of the method forcontrolling the attachment unit according to one embodiment of theinvention.

When the calibration start command is received in step 850, theattachment unit 410 may execute a calibration mode in step 910 and waitfor a command from the monitoring unit 420 in step 920.

Here, when a calibration end command is received in step 930, theattachment unit 410 may return to step 840 and wait for a command fromthe monitoring unit 420. Further, when a gain adjustment command isreceived in step 940, the attachment unit 410 may adjust the gain instep 950. Here, the gain adjustment command may include a command toincrease or decrease the gain, and the attachment unit 410 may increaseor decrease the gain according to the gain adjustment command.

When the measurement start command is received in step 860, theattachment unit 410 may execute a measurement mode in step 960. Forexample, the attachment unit 410 may emit light of a near-infraredregion using a laser or a light emitting diode (LED) through a source(S) included in the light transmission unit 411, and detect the emittedlaser or light through a detector (D) included in the light receptionunit 412.

When a measurement end command is received in step 970, the attachmentunit 410 may terminate the control method. In step 870, the attachmentunit 410 may also terminate the control method according to the systemoff command.

FIGS. 10 and 11 are flowcharts showing the control method for the casewhere firmware includes a function of determining how to adjust theseparation and gain of a channel according to one embodiment of theinvention.

First, FIG. 10 shows a process in which the attachment unit 410 adjuststhe gain of each channel under the control of the firmware 413 baccording to the calibration start command in step 850.

In step 1012, the attachment unit 410 may determine the number ofmaximum values, upper/lower boundary values, and a reference value.

In step 1014, the attachment unit 410 may separate information for eachchannel by n pieces of data. For example, the attachment unit 410 mayseparate the channel information by 16 pieces of data.

In step 1016, the attachment unit 410 may determine a maximum value pern pieces of data separated for each channel.

In step 1018, the attachment unit 410 may determine whether the numberof the determined maximum values is equal to a predetermined number ofmaximum values. For example, the attachment unit 410 may separate thechannel information by 16 pieces of data to determine the predeterminednumber of maximum values.

In step 1020, the attachment unit 410 may calculate an average of thedetermined maximum values.

In step 1022, the attachment unit 410 may determine whether the averagevalue (i.e., the average of the maximum values) is equal to or greaterthan the reference value. The attachment unit 410 may perform step 1024when the average value is equal to or greater than the reference value,and perform step 1026 when the average value is less than the referencevalue.

In step 1024, the attachment unit 410 may perform step 1030 when theaverage value is equal to or greater than the upper boundary value, andperform step 1028 when the average value is less than the upper boundaryvalue.

In step 1026, the attachment unit 410 may perform step 1030 when theaverage value is equal to or less than the lower boundary value, andperform step 1028 when the average value is greater than the lowerboundary value.

In step 1028, the attachment unit 410 may adjust the gain. For example,the attachment unit 410 may decrease the gain when the average value isequal to or greater than the reference value and less than the upperboundary value. Further, the attachment unit 410 may increase the gainwhen the average value is less than the reference value and greater thanthe lower boundary value. After adjusting the gain, the attachment unit410 may perform step 1014 again.

In step 1030, the attachment unit 410 may update the calibration stateof each channel. For example, the attachment unit 410 may update thecalibration state of each channel when the average value is equal to orgreater than the reference value and equal to or greater than the upperboundary value, or when the average value is less than the referencevalue and equal to or less than the lower boundary value.

In step 1032, the attachment unit 410 may return to step 840 and waitfor a command from the monitoring unit 420 when the calibration iscompleted for all channels. When the calibration is not completed forall channels, step 1014 may be performed.

Referring to FIG. 11, the attachment unit 410 may execute themeasurement mode in step 1110 upon receipt of the measurement startcommand in step 860, and separate the channels in step 1120. In step1130, the attachment unit 410 may terminate the control method uponreceipt of the measurement end command, or perform step 1110 again toexecute the measurement mode.

FIG. 12 shows an example of a headset system according to one embodimentof the invention.

A photograph 1210 shows a headset system 1211 including holders that arespread at specified equal intervals. The light transmission module 500or the light reception module 600 may be attached to or detached fromthe holders of the headset system 1211. The headset system 1211 may beattached to a subject's head through coupling components such as abuckle and a band, and may obtain a biosignal of a living organism in aregion where the headset system 1211 is attached.

As shown in a picture 1220, the headset system 1211 may have aH-hexagonal structure (HHS) composed of a plurality of lighttransmission modules 500 and a plurality of light reception modules 600as a basic structure. The HHS may be freely expanded to cover the entirehead based on the basic structure, as described with reference to thesecond configuration 720 of FIG. 7. In the picture 1220, T and R maydenote the light transmission module 600 and the light reception module700, respectively.

FIG. 13 shows an example of an expanded form of a headset systemcomposed of three basic structures according to one embodiment of theinvention, and FIG. 14 shows an expanded example of a headset systemcomposed of nine basic structures according to one embodiment of theinvention. FIG. 13 shows a headset system configured to measure abiosignal of a frontal lobe region in a human head, and FIG. 14 shows aheadset system configured to measure a biosignal from the entire humanhead. Here, the headset system may be attached to the measured region ofthe living organism through a buckle and a band.

Pipeline-Structured Matched Filter and Dual Slope Analog-DigitalConverter

FIG. 15 is a block diagram of Tx and Rx to which a matched filter for anoptical spectroscopy system is applied according to one embodiment ofthe invention. FIG. 15 shows how a matched filter 1511 is applied to Txand Rx 1510 of the optical spectroscopy system (particularly, theattachment unit 410 described with reference to FIG. 4). A laser isdriven based on the same clock (CLK) to inject light to a brain, and thelight attenuated as transmitted through the brain may be amplified usinga trans-impedance amplifier (TIA) and a programmable gain amplifier(PGA), and then digitized through the matched filter 1511 and a slopeanalog-digital converter (ADC) 1512. In this process, the time delaybetween the transmitted and received signals is negligible because it isvery short compared to the duration of Walsh codes. Since the form ofnoise caused by the scattering occurring in the transmission is the sameas that of white Gaussian noise, the influence of the noise can beminimized through the matched filter 1511.

FIG. 16 is a block diagram schematically showing an example in which amatched filter and a slope analog-digital converter are combinedaccording to one embodiment of the invention.

When a matched filter is used, a capacitor 1610 having a considerablylarge value should be connected to accumulate electric charge in thecapacitor 1610 as shown in FIG. 16. An output of the capacitor 1610 isgradually increased as current proportional to input voltage flows froman output of a transconductor (Gm) amplifier to the capacitor 1610 whileSW1 is 1. The electric charge stored in the capacitor 1610 is graduallydecreased through the current source from the time when SW1 becomes 0and SW2 becomes 1, and the time when the differential signals cross eachother is detected using the duration in which the comparator ismaintained at 1 based on the CLK. In the duration, the counter operatesbased on the clock and converts the time into digital codes, which maybe referred to as a slope ADC structure. Since the slope ADC structureimplemented after the matched filter can realize the ADC without theneed for additional capacitors, it is effective in terms of size and hasa high degree of integration in implementing a multi-channel receiver.

FIG. 17 shows an example of a matched filter applied in a pipelinestructure according to one embodiment of the invention, and FIG. 18shows a time diagram in the matched filter applied in the pipelinestructure according to one embodiment of the invention.

When one capacitor is used, input data is stored in the capacitor ineven phases and the stored charge is extracted in odd phases. Thus,since the capacitor cannot store the input data in odd phases, therearises a problem that the matched filter structure should be implementedusing only half of a bit period of inputted Walsh codes.

Accordingly, a switch-based pipeline structure is realized at a voltagenode by modifying the last stage within the transconductor (Gm) into apipeline structure, as shown in FIG. 17. As shown in FIG. 18, when acapacitor 1 (C1) is in the phase in which electric charge is stored,discharging occurs in a capacitor 2 (C2), which may mean that thecapacitors can smoothly operate in the form of a dual slope ADC (SSADC). Since they are switched at the voltage node, there are no moreinstantaneously generated current leakage lines (which are caused bynon-ideal rising and falling edges of the switching time), and thus theycan operate without current leakage. This allows a matched filterstructure to be implemented for the same time as the bit period of theinputted Walsh codes, and minimizes current leakage and nonlineareffects occurring in the switching circuit by implementing the pipelinestructure at the voltage node.

FIG. 16 is a diagram showing a simplified model in which only one phaseplane of the pipeline structure is shown, and FIG. 17 shows the pipelinestructure based on the diagram. Even phases may correspond to the casewhere SW1 is 1, and odd phases may correspond to the case where SW2is 1. In both cases, it can be seen that an IN signal and SW1 and SW2signals are equally aligned as the inputs. This is because the edges arealigned since the signals are generated based on the same clock, and thematched filter structure can be implemented based on thesecharacteristics.

FIG. 19 shows a detailed schematic structure of a pipelinetransconductor (Gm) amplifier according to one embodiment of theinvention. While SW is turned on, current dependent on input voltage isaccumulated in a capacitor. For linear accumulation, the bandwidth of anoutput node of Gm-C should exist in a very low frequency band. To thisend, the size of the capacitor should be large and the Gm value of theamplifier should be small. Since the size of the capacitor cannot beinfinitely increased, it is necessary to implement the small value ofGm. The value of Gm can be reduced by dividing the amount of currentgenerated in the circuit according to the inputs by means of a pair ofinput MOSs, and keeping a mirror ratio small until the final outputstage. OUT1 and OUT2, which are outputs of the pipeline structure, mayaccumulate electric charge in capacitors on the left side in a firstdashed line box 1910 when SWP is 1, and in capacitors on the right sidein the first dashed line box 1910 when SWN is 1. As above, one commonmode feedback circuit may be used such that it is switched for eachphase, thereby reducing the size of the matching circuit.

FIG. 20 shows a structure for calibrating a DC offset caused by a Gm-Cmismatch according to one embodiment of the invention.

A Gm-C amplifier itself is a MOS-based amplifier and needs to beprepared for a size mismatch between differential MOSs, which occurswhile proceeding with the process. To this end, in the periods excludingthe time when electric charge is accumulated in and drained fromcapacitors, a switch for mismatch calibration is used to sample theoffset when SW_MIS is 0 and SW_CM is 1, and then connected in theopposite phase when SW_MIS is 1 and SW_CM is 0, thereby enablingcompensation for the mismatch.

FIG. 21 shows a dual current source structure for discharge in apipeline Gm-C structure according to one embodiment of the invention.

A slope ADC performs its operation as electric charge accumulated incapacitors is discharged at different times in the form of a pipeline.If one current source is used to drain the charge, the differentcapacitors are connected to the current source through a SW-basedmultiplexer, or to a common voltage source Vref. In this case, since themultiplexer is a MOS-based SW and its resistance is not infinitely largein an OFF state, a current leakage phenomenon occurs so that the chargeleaks in the charge accumulation phase. Accordingly, as shown in FIG.21, two different current sources 2110 and 2020 may be connected to therespective capacitors for the pipeline to prevent the current node frombeing shared.

FIG. 22 shows a switching time diagram for a pipeline Gm-C based matchedfilter structure according to one embodiment of the invention. FIG. 22shows an example in which switching signals required to configure thepipeline structure are implemented by a clock generator that isdigitally synthesized based on a single clock (CLK).

A method for controlling the optical spectroscopy system according toone embodiment of the invention may comprise the following steps (1) and(2).

In the step (1), a pipeline-structured matched filter included in theoptical spectroscopy system may sequentially connect input voltage,which is transmitted through an amplifier, to a first capacitor and asecond capacitor through a first switch stage.

In the step (2), a dual slope analog-digital converter included in theoptical spectroscopy system may sequentially receive electric chargestored in the first and second capacitors through a second switch stageand digitize the input voltage.

Here, the first and second switch stages may sequentially switch theconnection to the first and second capacitors based on a clock generatedaccording to a Walsh code bit period, and may be connected to thedifferent capacitors among the first and second capacitors at the sameclock, respectively.

According to another embodiment of the invention, the method forcontrolling the optical spectroscopy system may further comprise thesteps of (3) emitting light to a specific region of a subject based onthe clock generated according to the Walsh code bit period, and (4)collecting light coming through the specific region, in addition to thesteps (1) and (2). Here, the steps (3) and (4) may be performed beforethe above-described steps (1) and (2), and may be performed by a lighttransmission unit (e.g., the light transmission unit 411) and a lightreception unit (e.g., the light reception unit 412), respectively. Here,the matched filter and the dual slope analog-digital converter may beincluded in the light reception unit and operated based on the clockused in the light transmission unit.

The light reception unit may comprise a TIA (Trans-Impedance Amplifier)and a PGA (Programmable Gain Amplifier) as the above-describedamplifier.

According to yet another embodiment of the invention, the method forcontrolling the optical spectroscopy system may comprise the step of (5)switching input voltage transmitted through the amplifier in each phaseand sequentially connecting the input voltage to a first capacitor and asecond capacitor, and sequentially receiving electric charge stored inthe first and second capacitors according to the phase and digitizingthe input voltage, instead of the above-described steps (1) and (2). Forexample, the step (5) may be performed by the common mode feedbackcircuit described with reference to FIG. 19.

According to still another embodiment of the invention, the method forcontrolling the optical spectroscopy system may further comprise thestep of (6) compensating for a size mismatch between differential MOSsin periods excluding the time when the first and second capacitors arecharged and discharged. The step (6) may be performed by a mismatchadjustment switch stage and a mismatch adjustment capacitor, which maybe further included in the optical spectroscopy system. For example, theinput voltage includes first voltage and second voltage, which areoutputs of the amplifier, and when the first input voltage is 1 and thesecond input voltage is 0, the mismatch adjustment switch stage maysample a DC offset size existing in the amplifier itself to the mismatchadjustment capacitor, and then connect the sampled voltage to the firstand second capacitors in the opposite phase, thereby compensating forthe size mismatch between the differential MOSs.

Optical Spectroscopy System Operating as a Walsh Code-Based Single CLKGenerator

An optical spectroscopy system according to the present embodiments mayuse a Walsh code-based single CLK generator. As for Walsh codes, whichare among the codes used for code division multiplexing, the number oforthogonal codes is determined according to the code length, and thecorrelation between the codes is zero.

Thus, when the Walsh codes are used to modulate a sequence of lasers oflight transmission modules in the optical spectroscopy system, one lightreception module can demodulate and extract hemodynamics information ofvarious regions without interference between channels.

FIG. 23 shows an example of an application aspect of CDMA modulationaccording to one embodiment of the invention.

In FIG. 23, when light emitted from a source 1 (S1) and a source 2 (S2)passes through a living organism and enters a detector, it is notpossible to distinguish the light emitted from S1 and that emitted fromS2 according to a principle of near-infrared spectroscopy (NIRS). Thus,in the optical spectroscopy system according to the embodiments of theinvention, light can be emitted from each light source as code-modulatedwith perfectly orthogonal codes (e.g., the above-described Walsh codes).

Further, the light emitted from the detector can be demodulated with thesame codes as those of the light source, so that it is possible todistinguish which light source has emitted the light. In this manner,the optical spectroscopy system can use light entering a detector from aplurality of light sources to accurately determine which part of thebrain is activated to change the concentrations of oxyhemoglobin andincident light.

TABLE 1 shows the factors that cause changes in an oxygen saturationlevel in human blood and information on the corresponding frequencybands.

TABLE 1 Freq. No. Artifact Source (Hz) 1 Laser temperature driftTemperature dependency of laser 2 Very low frequency — 0.04 oscillation3 Low freq. spontaneous Relate to arterial blood 0.1 physiologicaloscillations pressure (LFO, vasomotor wave, or Mayer's wave) 4Respiration frequency Respiration 0.2 (Adult: 12-20 cycle/min) 5 Cardiacoscillation Heart beat (Adult: 60-80) 1

The changes in the blood oxygen saturation level occurring in a humanbody are caused by the factors shown in TABLE 1, and it can be seen thatthe changes are considerably slow since they are not more frequent than1 Hz.

FIG. 24 shows an example of an aspect of modulating changes in a bloodoxygen saturation level with codes according to one embodiment of theinvention. First, the following parameter values should be determined inorder to measure signals using a code-based modulation technique in theoptical spectroscopy system.

The chip rate and length of the codes used for the modulation may bedetermined in consideration of the symbol rate at the time ofdemodulation and the hemodynamic frequency in the human body. Assumingthat a unit Walsh code modulation sequence is repeated and that there islittle change in the oxygen saturation level, the result of demodulationin the received signals can be obtained because it is possible tocorrectly recover the signals in the body. Further, the chip rate andunit code length may be adjusted according to the number of channels tobe independently received and the specifications of the system.

FIG. 25 shows an example of a flowchart for extracting a hemodynamicsignal except for low noise when proceeding with code-based modulationand demodulation according to one embodiment of the invention.

The form of laser light modulated with Walsh codes is changed accordingto a hemodynamic change in a path through which the light travels fromwhen it enters a living body until it is detected by a detector. It canbe said that the form corresponds to the Walsh codes being mixed withthe hemodynamic signals. Although hemodynamic information corresponds tosignals of less than about 1 Hz, the Walsh codes of a higher frequencyband are used and thus the tones of the signals move to a high frequencyband. Accordingly, when an operation related to analog amplification isperformed in a chip, there is immunity to 1/f noise components, whichare large noises of a low frequency band generated in the circuititself. After a demodulation process, the noise-minimized hemodynamicsignals may be extracted through low pass filtering (similarly to achopping structure).

Matched Filter-Based Data Sampling

White noises existing in input signals and circuits may be accumulatedin a continuous time domain based on an oversampling effect, so that onepiece of data may be extracted for each bit period. This technology isemployed for optical communication systems, and uses a matched filterstructure that can extract a signal with a maximum signal-to-noise ratio(SNR). In order to implement the matched filter structure, there is aprecondition that bits received as inputs should be exactly synchronizedwith a sampling clock. Thus, in the optical communication systems, theclock is controlled by further using a phase locked loop (PLL) at areception stage.

However, in the embodiments of the invention, a signal separated byusing a reference clock in an integrated circuit itself is injected intoa subject's head, and the injected signal is transmitted through thesubject's head to a receiver (e.g., the light reception module 600).(That is, light emission and detection are both performed in onesystem.) Therefore, accumulation periods may be generated in the samesynchronization using the same separated signal in the integratedcircuit, so that the matched filter may be implemented with a simplerstructure.

As an oversampling rate N is increased, the noise of a measured signalis reduced to 1/square root N. Since the result of infinitely increasingN is the same as the accumulated form, the white Gaussian noisegenerated within the signals and the chip (integrated circuit) may bemaximally reduced.

FIG. 26 shows an oversampling effect and a matched filter effectaccording to one embodiment of the invention, and FIG. 27 shows acomparison between a matched filter structure of prior art and thataccording to one embodiment of the invention.

In order to implement a matched filter structure, there is aprecondition that signals received as inputs should be exactlysynchronized with a clock used in sampling. In a general communicationsystem (a system 2710 of prior art), a reference clock is external to areceiver, and the receiver should further use additional circuitry suchas a PLL to adjust sampling synchronization in order to synchronize withthe data received at an input of the receiver. However, in an integratedcircuit of an optical spectroscopy system 2720 according to the presentembodiment, a modulation sequence is generated using a reference clockof the integrated circuit itself, and the generated signal only has itsown attenuation while it is injected into a brain channel of a subject(corresponding to an external system of prior art) and then transmittedthrough a cerebral cortex to a receiver. Accordingly, it can be assumedthat the received input signals are synchronized with the sampled clock,and thus the function of the matched filter can be implemented with arelatively simple structure in the optical spectroscopy system 2720according to the present embodiment.

A method for controlling the optical spectroscopy system according toone embodiment of the invention may comprise the steps of emitting lightto a specific region of a subject using a plurality of light sources ina light transmission unit (e.g., the light transmission unit 411)included in the optical spectroscopy system, wherein the light emittedfrom the plurality of light sources is code-modulated using Walsh codes,and detecting light coming through the specific region in a lightreception unit (e.g., the light reception unit 412) included in theoptical spectroscopy system, wherein the light is demodulated using theWalsh codes to distinguish the light sources. Here, the control methodmay further comprise the step of extracting one piece of data for eachbit period by accumulating input signals in a continuous time domainusing a reference clock used for the light emission in a matched filterincluded in the light reception unit as a sampling clock.

A method for controlling the optical spectroscopy system according toanother embodiment of the invention may comprise the steps of emittinglight to a specific region of a subject in a light transmission unit ofthe optical spectroscopy system, and detecting light coming through thespecific region in a light reception unit of the optical spectroscopysystem. Here, in the step of detecting light, a matched filter includedin the light reception unit may extract one piece of data for each bitperiod by accumulating input signals in a continuous time domain using areference clock used for the light emission as a sampling clock.

The matched filter of each embodiment may match bits received as inputswith light emitted using the reference clock, so that synchronizationbetween the bits received as inputs and the reference clock may beachieved without using any additional PLL.

Optical Spectroscopy System Using Time-Divided Spread Spectrum Codes(TDSSC)

Depending on the type of person, the degree of light absorption varieswith the curvature of the head, the thickness of layers constituting thehead, the color of skin, and the like. Thus, if the same laser power isapplied to the entire region of the head and to all persons, a situationmay occur in which light transmitted through a cerebrum in a specificmeasured region is all absorbed before reaching the surface of the head,so that the measurement may not be possible. In this regard, it ispossible to allow the light transmitted through the cerebrum to reachthe surface of the head by making the laser power strong. However, thelaser power cannot be infinitely increased because there is a limitationon the power of laser that can be maximally injected into the humanbody.

FIG. 28 shows an application example of time-divided spread spectrumcodes according to one embodiment of the invention. As described above,since light injected into a human body may be represented as the numberof photons per unit time, intense light may be injected into the humanbody if the duration in which the light is injected is adjusted so thata small amount of photons are instantaneously injected. Thus, thephotons can reach the surface of the head by increasing theinstantaneous intensity of the light while maintaining the entire amountof energy. Further, it is possible to design the system so that moreintense light is injected into the human body while reducing theduration of 1 of Walsh codes per unit time. For example, if an on/offduty ratio is adjusted on the assumption that the same energy isinjected, spread codes are simultaneously started and injected and thensimultaneously turned off, thereby maintaining the orthogonality betweenthe codes. It is assumed in FIG. 28 that on/off duty ratios are 1 and0.5 in Cases 1 and 2, respectively. Laser injection time for the dutyratio of 0.5 is twice as small as that for the duty ratio of 1, so thatthe signal magnitude of the injected Walsh codes can be relativelyincreased (P2=P1×2). The time-divided spread spectrum codes (TDSSC) maybe implemented with a structure capable of adjusting the duty of Walshcodes and laser power within the integrated circuit.

Multi-Channel Laser and LED Driver

In the light transmission module according to the present embodiment, itis possible to adjust power from 5.2 mA to 14.9 mA in 256 stages with adual wavelength laser and a LED driver. Further, there is an option todouble the scale, and it is possible to output signals modulated withWalsh codes according to each wavelength.

FIG. 29 shows structures of a dual wavelength laser driver and a LEDdriver according to one embodiment of the invention. FIG. 29 shows adual wavelength laser driver 2910, which is a dual VCSEL (VerticalCavity Surface Emitting Laser) device, and a dual wavelength LED driver2920, which is a dual LED device. Here, the dual wavelength laser driver2910 and the dual wavelength LED driver 2920 may be connected to a phaseof one of positive and negative electrodes. In FIG. 29, the dualwavelength laser driver 2910 is connected to ground together with thepositive electrode, and the dual wavelength LED driver 2920 is connectedto VDD together with the negative electrode. Thus, in order to modulatethe dual wavelength laser driver 2910 (i.e., the dual VCSEL) and thedual wavelength LED driver 2920 with different codes, they should beimplemented using different drivers.

FIG. 30 shows a drive control signal level shifter according to oneembodiment of the invention. A drive control signal level shifter 3000may change a control voltage domain in a circuit using 3.3V as VDD inorder to cover forward voltage of a laser (e.g., the dual wavelengthlaser driver 2910) and a LED (e.g., the dual wavelength LED driver2920). A start-up circuit 3010 may be connected to the drive controlsignal level shifter 3000 to allocate basic voltage of each node whenpower is initially turned on.

FIG. 31 shows a laser driver using time-divided spread spectrum codesaccording to one embodiment of the invention. A dual laser driver 3110may operate in conjunction with the other components shown in FIG. 31.First, a Walsh code generator (128 Walsh Code GEN) 3120 may generate 128independent Walsh codes based on a reference clock outputted from aclock generator (CLK GEN) 3130. The Walsh codes to be used may beselected from the 128 Walsh codes as desired by a user, and the selectedWalsh codes may be boosted from 1.8V to 3.3V by a level shifter 3130 andthen applied to the laser driver 3110 as input signals. A duty controlsignal may be applied from a microcontroller unit (MCU), and on/off of alaser drive signal may be adjusted in a time domain by the duty controlsignal.

A method for controlling the optical spectroscopy system according tothe present embodiment may comprise the steps of emitting light to aspecific region of a subject through a light source in a lighttransmission unit (e.g., the light transmission unit 411) included inthe optical spectroscopy system, wherein total energy is maintainedconstant by decreasing the time of emitting the light and increasing theintensity of the light, and collecting light coming through the specificregion in a light reception unit (e.g., the light reception unit 412)included in the optical spectroscopy system. Here, the lighttransmission unit may decrease an on/off duty ratio of the lightemission by a predetermined ratio using time-divided spread spectrumcodes, and increase the intensity of the light by the predeterminedratio. Otherwise, the light transmission unit may decrease unit durationof Walsh codes per unit time by a predetermined ratio using time-dividedspread spectrum codes, and increase the intensity of the light by thepredetermined ratio. The light source may comprise a dual wavelengthlaser device and a dual wavelength LED device, and may further comprisea level shifter for changing a control voltage domain of a circuitincluding the laser device and the LED device. Here, the step ofemitting light may comprise the steps of boosting, through the levelshifter, a signal corresponding to a code to be used among apredetermined number of mutually independent Walsh codes generated basedon a reference clock, and receiving the boosted signal in the laserdevice as an input signal and adjusting on/off of the input signal usinga duty control signal applied from a MCU.

Monitoring Unit

Information obtained by the attachment unit 410 described with referenceto FIG. 4 may be processed, visualized, and controlled by the monitoringunit 420. The monitoring unit 420 may be implemented using a devicehaving a display, such as a computer, a notebook, a smart phone, a smartwatch, and a tablet PC.

The monitoring unit 420 may include functions for the following (1) to(5).

(1) Optical data of a plurality of wavelengths of each channel separatedby firmware (e.g., the firmware 413 b of FIG. 4) may be received throughwireless communication.

(2) The received data may be processed through digital signalprocessing. For example, the monitoring unit 420 may process thereceived data through a low pass filter and a laser temperature driftrejection process.

(3) The processed data may be converted into a concentration changevalue of oxyhemoglobin and that of deoxyhemoglobin through calculationof the modified Beer-Lambert law.

(4) The concentration change values of oxyhemoglobin and deoxyhemoglobinmay be displayed in color on a three-dimensional map.

(5) When the release of a new version of firmware is recognized, thefollowing processes are performed: (a) switching to a firmware updatescreen of a mobile application (hereinafter, “mobile app”) of themonitoring unit 420, (b) entering a firmware update mode of a hardwareboot loader, and (c) uploading new firmware.

The release of a new version of firmware is recognized by the followingmethods (a) and (b).

(a) When the mobile app is executed, it connects to a server andperforms user and version check. When the release of a new version offirmware is recognized, it guides the subsequent update.

(b) Whether a new version of firmware is released is notified through apush alarm or other corresponding alarm methods, and the subsequentupdate is guided.

FIG. 32 is a flowchart showing an example of a method for automaticfirmware update according to one embodiment of the invention, and FIG.33 shows functions for updating firmware according to one embodiment ofthe invention.

In step 3210, the web server 440 may determine whether a serial numberof a device is equal to a serial number stored in a database (DB) of theweb server 440. To this end, the web server 440 may register the serialnumber of the device (or the attachment unit). Step 3220 may beperformed when the serial number of the device is equal to theregistered serial number, and firmware update may be terminated whenthere is no registered serial number equal to the serial number of thedevice.

In step 3220, the web server 440 may determine whether a firmwareversion of the device is lower than the currently available firmwareversion. The web server 440 may release a new version of firmware andnotify the monitoring unit 420 of the release of the new version offirmware.

In step 3230, the monitoring unit 420 may download the firmware from theweb server 440. Further, in step 3240, the monitoring unit 420 may beconnected to the attachment unit 410. The monitoring unit 420 may act asa bridge between the web server 440 and the attachment unit 410, and maycontrol the attachment unit 410 to update the firmware.

In step 3250, the attachment unit 410 may execute a firmware updatemode. Further, in step 3260, the attachment unit 410 may download thefirmware from the monitoring unit 420.

In step 3270, the attachment unit 410 may determine whether any errorexists in the downloaded firmware. Step 3260 may be performed again whenany error exists, and step 3280 may be performed when no error exists.As above, the attachment unit 410 may include a function of checkingerrors in the downloaded firmware.

In step 3280, the attachment unit 410 may execute the reset and updatedfirmware.

Big Data Analysis

FIG. 34 shows functions for processing big data according to oneembodiment of the invention. The web server 440 may collect data on ananonymous subject who has consented from the user server 430 and performbig data analysis as follows:

(1) The user server 430 may inquire of a subject whether or not toprovide measured data to the web server 440. For example, the userserver 430 may provide the measured data to the web server 440 with theconsent of the anonymous subject.

(2) When the anonymous subject consents to information provision in theuser server 430, the web server 440 may anonymously collect the measureddata from the user server 430.

(3) The web server 440 may accumulate the measured data of the anonymoussubject, classify the accumulated data, and analyze the classified data.

(4) The web server 440 may provide personalized results of big dataanalysis on the personal measurement data to the monitoring unit 420through the user server 430, only for the subject who has consented tothe information provision, and the monitoring unit 420 may provide areport optimized for the user (e.g., display it on a screen).

Through the application of the big data analysis, it is possible todetect a symptom early from the measurement results of the user bycomparing the results obtained from a conventional apparatus or anoptical spectroscopy system regarding a specific disease such as astroke.

In addition, information on various diseases that has not beenrecognized before may be accumulated based on measurement results in asimilar environment, and the accumulated information may be used toanalyze a wider range of data and detect a symptom of a disease.

Further, through the accumulation and analysis of personal measurementdata, it is possible to continuously monitor the changes in patients whohave a high likelihood of recurrence and need continuous management, sothat risk factors may be discovered in advance. In other words, it ispossible to continuously accumulate personal measurement data toconstruct personal big data, and to compare and analyze the big data todiscover any risk factor in the current measurement result of the useror provide a report optimized for the user regarding any recognizedchanges.

Furthermore, for the same reasons as the above, it is possible toaccumulate and recognize personal measurement data when it is necessaryto recognize the effects of gradual changes (e.g., duringrehabilitation), and to develop a personal rehabilitation program.

As described above, according to the embodiments of the invention, it ispossible to provide a mobile and expandable firmware-based opticalspectroscopy system and a method for controlling the same.

Further, it is possible to use a pipeline-structured matched filter toimplement a matched filter structure for the same time as a bit periodof input Walsh codes, and minimize current leakage and nonlinear effectsoccurring in a switching circuit.

Further, it is possible to use time-divided spread spectrum codes(TDSSC) to reduce duration of 1 of Walsh codes per unit time and injectmore intense light, thereby increasing the intensity of the light withthe same total energy.

Further, it is possible to modulate light emitted from a plurality oflight sources using Walsh codes and emit the modulated light, and detectlight coming through a specific region and demodulate the detected lightusing the Walsh codes, thereby distinguishing the light source that hasemitted the light.

Further, it is possible to accumulate input signals using a referenceclock used for light emission as a sampling clock, thereby minimizingwhite Gaussian noise without additional circuitry such as an additionalphase locked loop (PLL).

Further, it is possible to process, visualize, and control data in amonitoring device, and guide firmware update according to the release ofa new version of firmware included in an attachment device such as aheadset.

Further, it is possible to collect, manage, and analyze data measuredthrough a web server and provide personalized results through amonitoring device.

The above-described devices (i.e., the optical spectroscopy system 400,the attachment unit 410, the monitoring unit 420, the user server 430,and the web server 440) may be implemented with hardware components,software components, and/or a combination of hardware and softwarecomponents. For example, the devices and components described in theembodiments may be implemented using one or more general or specialpurpose computers, such as a processor, a controller, an arithmeticlogic unit (ALU), a digital signal processor, a microcomputer, a fieldprogrammable array (FPA), a programmable logic unit (PLU), amicroprocessor, or any other device capable of executing and respondingto instructions. The processing device may execute an operating system(OS) and one or more software applications running on the operatingsystem. Further, the processing device may also access, store,manipulate, process, and generate data in response to the execution ofthe software. For ease of understanding, the processing device may bedescribed as being used singly, but those skilled in the art willappreciate that the processing device may include a plurality ofprocessing elements and/or a plurality of types of processing elements.For example, the processing device may comprise a plurality ofprocessors or one processor and one controller. Further, otherprocessing configurations such as a parallel processor are alsopossible.

The software may comprise computer programs, codes, instructions, or acombination of one or more of the foregoing, and may configure theprocessing device to operate as desired or instruct the processingdevice independently or collectively. Software and/or data may bepermanently or temporarily embodied in any type of machine, component,physical device, virtual equipment, computer storage medium or device,or a transmitted signal wave, so that the software and/or data may beinterpreted by the processing device or may provide instructions or datato the processing device. The software may be distributed over networkedcomputer systems, and may be stored or executed in a distributed manner.The software and data may be stored on one or more computer-readablerecording media.

The method according to the embodiments of the invention may beimplemented in the form of program instructions that can be executed byvarious computer means, and may be stored on a computer-readablerecording medium. The computer-readable recording medium may includeprogram instructions, data files, data structures and the like,separately or in combination. The program instructions stored on themedium may be specially designed and configured for the embodiments, ormay also be known and available to those skilled in the computersoftware field. Examples of the computer-readable recording mediuminclude the following: magnetic media such as hard disks, floppy disksand magnetic tapes; optical media such as compact disk-read only memory(CD-ROM) and digital versatile disks (DVDs); magneto-optical media suchas floptical disks; and hardware devices such as read-only memory (ROM),random access memory (RAM) and flash memory, which are speciallyconfigured to store and execute program instructions. Examples of theprogram instructions include not only machine language codes created bya compiler or the like, but also high-level language codes that can beexecuted by a computer using an interpreter or the like. The abovehardware devices may be configured to operate as one or more softwaremodules to perform the processes of the embodiments, and vice versa.

Although the embodiments have been described in terms of the limitedembodiments and drawings, those skilled in the art can make variousmodifications and changes from the above description. For example,appropriate results can be achieved even if the described techniques areperformed in a different order than the described methods, and/or thecomponents of the described systems, structures, devices, circuits, andthe like are coupled or combined in a different form than the describedmethods, or changed to or replaced with other components or equivalents.

Therefore, other implementations, other embodiments, and equivalents tothe appended claims also fall within the scope of the following claims.

What is claimed is:
 1. An optical spectroscopy system, comprising: anattachment unit attached to a specific region of a subject andconfigured to, based on firmware, emit light to the specific region andcollect light coming through the specific region to measure a biosignalof the subject; and a monitoring unit connected to the attachment unitthrough a wired or wireless network and configured to control anintensity of the light emitted by the attachment unit.
 2. The opticalspectroscopy system of claim 1, wherein the attachment unit comprises: alight transmission unit configured to emit light to the specific regionusing at least one of a laser and a light emitting diode (LED); a lightreception unit configured to detect light coming through the specificregion; and a main processing unit configured to control the lighttransmission unit and the light reception unit based on the firmware,and receive output data of the light reception unit.
 3. The opticalspectroscopy system of claim 2, wherein the firmware includes: (1) afunction for controlling operations of the light transmission unit, thelight reception unit, and the main processing unit; (2) a function forseparating the output data received by the main processing unit from thelight reception unit into optical data of each channel; and (3) afunction for controlling the attachment unit to transmit the separatedoptical data to the monitoring unit.
 4. The optical spectroscopy systemof claim 3, wherein the firmware further includes: (4) a function forproviding a firmware update mode to update the firmware and a firmwareexecution mode to execute the firmware.
 5. The optical spectroscopysystem of claim 3, wherein a plurality of light transmission modulesincluded in the light transmission unit emit light of different channelsmodulated with time-divided spread spectrum codes (TDSSC), and whereinthe firmware demodulates data for the light received by the lightreception unit based on the time-divided spread spectrum codes toseparate the output data into the optical data of each channel.
 6. Theoptical spectroscopy system of claim 2, wherein the light transmissionunit comprises a plurality of light transmission modules, and whereineach of the plurality of light transmission modules comprises: a lightsource including at least one of a laser and a light emitting diode(LED); a cylinder in which the light source is inserted; a springconfigured to provide physical pressure to the cylinder in which thelight source is inserted, such that the light source is brought intoclose contact with the specific region of the subject; and a case withinwhich the light source, the cylinder, and the spring is disposed.
 7. Theoptical spectroscopy system of claim 6, wherein each of the plurality oflight transmission modules further comprises: a reference lightreception unit disposed on a side surface of the cylinder within thecase and configured to collect light coming through the specific region.8. The optical spectroscopy system of claim 2, wherein the lightreception unit comprises a plurality of light reception modules, andwherein each of the plurality of light reception modules comprises: alight detector configured to collect light coming through the specificregion; a cylinder in which the light detector is inserted; a springconfigured to provide physical pressure to the cylinder in which thelight detector is inserted, such that the light detector is brought intoclose contact with the specific region of the subject; and a case withinwhich the light detector, the cylinder, and the spring is disposed. 9.The optical spectroscopy system of claim 8, wherein each of theplurality of light reception modules further comprises a trans-impedanceamplifier (TIA) inserted in the cylinder together with the lightdetector, and wherein the light collected by the light detector isconverted into an electrical signal and amplified by the TIA in a fullydifferential manner.
 10. The optical spectroscopy system of claim 1,wherein in the attachment unit, an additional function is added to theattachment unit by updating the firmware.
 11. The optical spectroscopysystem of claim 1, wherein in the attachment unit, an area in which thebiosignal is measurable is expanded by adding a basic structure, whichis a H-hexagonal structure (HHS) composed of a plurality of lighttransmission modules and a plurality of light reception modules.
 12. Theoptical spectroscopy system of claim 11, wherein when the basicstructure is added, the attachment unit updates the firmware to add anexpanded function according to the added basic structure.
 13. Theoptical spectroscopy system of claim 1, wherein the attachment unit isimplemented in the form of a headset attachable to a head region of thesubject.
 14. The optical spectroscopy system of claim 1, furthercomprising: a web server configured to provide a new version of firmwareand accumulate data for the biosignal to manage and analyze the data.15. A method for controlling an optical spectroscopy system, wherein theoptical spectroscopy system comprises an attachment unit and amonitoring unit, and wherein the method comprises the steps of: by theattachment unit, determining whether the attachment unit is connected tothe monitoring unit; by the attachment unit, initializing a system ofthe attachment unit according to a system on command; by the attachmentunit, adjusting a gain of each channel for light of different channelsemitted by the attachment unit, according to a calibration start commandfrom the monitoring unit; by the attachment unit, emitting light to aspecific region of a subject according to a measurement start commandfrom the monitoring unit, and collecting light coming through thespecific region to measure a biosignal of the subject; and by theattachment unit, terminating the system of the attachment unit accordingto a measurement end command or a system off command from the monitoringunit.
 16. The method of claim 15, wherein the step of adjusting a gainof each channel comprises: determining a number of maximum values forthe different channels, upper/lower boundary values, and a referencevalue; determining a maximum value per n pieces of data separated foreach of the channels; and increasing or decreasing the gain of eachchannel based on an average of the determined maximum values, thereference value, and the upper/lower boundary values.
 17. The method ofclaim 16, wherein in the step of increasing or decreasing the gain ofeach channel, the gain is decreased when the average of the determinedmaximum values is equal to or greater than the reference value and lessthan the upper boundary value, and the gain is increased when theaverage of the determined maximum values is less than the referencevalue and greater than the lower boundary value.
 18. The method of claim15, wherein in the step of adjusting a gain of each channel, the gain ofeach channel is adjusted under the control of firmware included in theattachment unit.
 19. The method of claim 15, wherein in the step ofadjusting a gain of each channel, the gain of each channel is adjustedaccording to an adjustment value received from the monitoring unit, andwherein the monitoring unit determines a number of maximum values forthe different channels, upper/lower boundary values, and a referencevalue; determines a maximum value per n pieces of data separated foreach of the channels; generates the adjustment value based on an averageof the determined maximum values, the reference value, and theupper/lower boundary values; and transmits the generated adjustmentvalue to the attachment unit together with a gain adjustment command.